As a cooling device, which cools a heat generating portion of an electronic apparatus, there is widely used a mechanism having: a heat receiving portion (heat spreader) which is thermally connected to the heat generating portion; a heat transporting member (heat pipe) in which one end portions is connected to the heat receiving portion; a heat exchanging portion (cooling fins) which is disposed in the other end portion of the heat transporting member; and air blower (cooling fan) for cooling the heat exchanging portion.
In an electronic apparatus such as a notebook personal computer, a cooling device which cools a semiconductor package is accommodated in a case. The cooling device is configured by a heat spreader, a heat pipe, a heat exchanging portion, and a fan unit. The heat exchanging portion has a plurality of thin plate-like fins in each of which a through hole is formed, and which are stacked at intervals of about several millimeters. A heat radiating end portion of the heat pipe is passed through the through holes of the fins, and thermally connected to the fins. The fan unit has a fan case having an inlet and an outlet, and a fan which is rotationally driven by a motor housed in the fan case. When the fan is rotated, the fan unit suctions the air in the axial direction of the fan, and discharges the sucked air in the centrifugal direction of the rotation.
When the heat exchanging portion is viewed toward the front side from the interior of the fan case, the heat exchanging portion shows an appearance in which end edges of the fins upstand and are arranged in multiple layers in a horizontal direction. FIG. 26 shows positional relationships between the heat exchanging portion and the fan unit, and a blowing air passage in the case where the heat exchanging portion and the fan unit are viewed from the upper side. In the heat exchanging portion 90, the fins 91 are located in the side of a fan outer peripheral portion 92 along the arrangement direction of the fins 91. In the fan case 94 of the fan unit 93, the blowing air passage is formed so that the air is blown from the fan outer peripheral portion 92 in the centrifugal direction of the rotation on a horizontal plane. An outlet 95 for the cooling air from the blowing air passage is opened in the end edges 96 of the fins 91 on the side of the air inlet side. The speed of the air flow flowing through the gap between two fins 91 which are positioned in the right side in the figure among the fins 91 is higher than that of the air flow flowing through the gap between two fins 91 which are positioned in the left side. Dusts contained in the cooling air easily adhere to the end edges 96 of the fins 91 of the right side. In the plane including the end edges 96, a portion 97 where dusts easily accumulate is positioned in the right side of the plane, in the case where the plane is viewed in the direction from the fan unit 93 toward the heat exchanging portion 90. Dusts first begin to accumulate in the portion 97. In the vicinity of the cooling device of the electronic apparatus, dusts accumulate during use, and there is a case where the dusts clog the air passage and the cooling performance of the apparatus is impaired.
In a notebook personal computer, the thickness of the case must be suppressed. In a state where a cooling device is disposed on a circuit board, the installation dimension of the cooling device is limited by the thickness of a case. The dimensions of a cooling fan and a heat exchanger are determined so that their heights and the unit height are reduced in the thickness direction of the case. Conventionally, an electronic apparatus is known in which, while satisfying requirements for reductions of the size and the weight, the efficiency of the heat control is improved so as to contribute to enhancement of the performance efficiency. An example of such electronic apparatus is disclosed in Japanese Patent No. 3,302,350 (counterpart U.S. publication is: U.S. Pat. No. 6,496,369 B2).
In a notebook personal computer, however, the space in the case is very limited, and the thickness of the case is restricted. In the example of FIG. 26, it is difficult to dispose a device for removing dusts adhering to the end edges 96 of the fins 91, between the heat exchanging portion 90 and the fan unit 93, because the space in the case is narrow, and the cooling air passage is blocked to increase the air flow resistance.